Power generation circuit using electromagnetic wave

ABSTRACT

A power generation circuit using an electromagnetic wave which does not require any additional energy is provided. Power generation is performed by utilizing the electromagnetic wave existing in a space for living.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a circuit that generates and storeselectric power by utilizing electromagnetic wave.

2. Description of the Related Art

A circuit of a non-contact IC card is shown in FIG. 12 as an example ofa conventional power generation circuits that utilize electromagneticwave (refer to JP 3418322 B, FIG. 11, for example).

An electromagnetic coupling coil 101 and an IC chip 102 are mounted on anon-contact IC card 100. An IC card reader/writer 103 has anelectromagnetic coupling coil 104 for electromagnetically coupling theelectromagnetic coupling coil 101 of the IC card 100. The IC card 100operates by using electric power supplied from the IC card reader/writer103 through the electromagnetic coupling.

In the conventional power generation circuit using electromagnetic wavehas a drawback in which means for supplying electric power is necessary.Further, there is a problem in that characteristics of an antenna maychange depending on a length of wiring for the antenna when mounted.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-mentionedproblems inherent in the conventional art. It is an object of thepresent invention to provide a power generation circuit capable ofgenerating electric power by receiving energy from electromagnetic wavewhich fills space for living.

According to the present invention, a power generation circuit usingenergy of electromagnetic wave includes: one of an antenna or a coil forreceiving an electromagnetic wave; a rectifying circuit formed on asilicon substrate, for rectifying a signal from the antenna or the coil;and a circuit for storing an output power from the rectifying circuit,wherein power generation is performed by utilizing the energy of theelectromagnetic wave; and the electromagnetic wave is a commerciallyavailable electromagnetic wave.

Further, the present invention provides a power generation circuit usingenergy of electromagnetic wave, in which a source and a drain of anenhancement MOS transistor are connected between an output of thestoring circuit and a load, and control of connecting the storingcircuit and the load is performed by utilizing the threshold voltage ofthe enhancement MOS transistor.

Still further, the present invention provides a power generation circuitusing energy of electromagnetic wave, in which; a recess is formed inthe silicon substrate; a projecting terminal which conforms to a shapeof the recess in the silicon substrate is formed on one of the antennaor the coil; and an electrical connection is established between theantenna and an element formed on the silicon substrate by inserting theprojecting terminal of the antenna or the coil into the recess in thesilicon substrate.

Yet further, the present invention provides a power generation circuitusing energy of electromagnetic wave, in which the electromagnetic waveexists in a space for living.

Furthermore, the present invention provides a power generation circuitusing energy of electromagnetic wave including: one of an antenna or acoil for receiving an electromagnetic wave; a rectifying circuit formedon a silicon substrate, for rectifying a signal from one of the antennaor the coil; a booster circuit for boosting an output of the rectifyingcircuit; a storage circuit for storing an output power from the boostercircuit; a detecting circuit for detecting a voltage of the storagecircuit; and a switching circuit for connecting the storage circuit anda load, wherein power generation is performed by utilizing the energy ofthe electromagnetic wave; and the switching circuit is turned on toconnect the storage circuit and the load when the detecting circuitdetects that the voltage of the storage circuit is equal to or greaterthan a predetermined voltage.

Further, the present invention provides a power generation circuit usingenergy of electromagnetic wave, including: one of an antenna or a coilfor receiving an electromagnetic wave; a rectifying circuit formed on asilicon substrate, for rectifying a signal from one of the antenna orthe coil; a booster circuit for boosting an output of the rectifyingcircuit; a storage circuit for storing an output power from the boostercircuit; a detecting circuit for detecting a voltage of the storagecircuit; a switching circuit for connecting the storage circuit and aload; and a mono-stable multi-vibrator circuit whose input is a signalfrom the detecting circuit, wherein power generation is performed byutilizing the energy of the electromagnetic wave; and the switchingcircuit is turned on for a defined period of time determined by themono-stable multi-vibrator circuit when the detecting circuit detectsthat the voltage of the storage circuit is equal to or greater than adefined voltage to connect the storage circuit and the load.

Further, the present invention provides a power generation circuit usingenergy of electromagnetic wave, including: one of a first antenna or afirst coil for receiving an electromagnetic wave of a first frequency; afirst rectifying circuit formed on a silicon substrate, for rectifying asignal from one of the first antenna or the first coil; a boostercircuit for boosting an output of the first rectifying circuit; anstorage circuit for storing an output power from the booster circuit; aswitching circuit for connecting the storing circuit and a load; one ofa second antenna or a second coil for receiving an electromagnetic waveof a second frequency different from the electromagnetic wave of thefirst frequency received by the first antenna or the coil; and a secondrectifying circuit formed on the silicon substrate, for rectifying asignal from one of the second antenna or the second coil, wherein one ofthe first antenna or the coil performs power generation by utilizing theenergy of the electromagnetic wave of the first frequency; the energy isstored in the storage circuit; and the switching circuit is turned on toconnect the storage circuit and the load, when power generation isperformed by the second rectifying circuit after receiving theelectromagnetic wave of the second frequency, which has a differentfrequency from the electromagnetic wave of the first frequency, by thesecond antenna or the second coil.

Moreover, the present invention provides a power generation circuitusing energy of electromagnetic wave, including: one of a first antennaor a first coil for receiving an electromagnetic wave; a first rectifiercircuit formed on a silicon substrate, for rectifying a signal from thefirst antenna or the first coil; a booster circuit for boosting anoutput from the first rectifying circuit; an storage circuit for storingan output power from the booster circuit; a switching circuit forconnecting the storage circuit and a load; one of a second antenna or asecond coil for receiving an electromagnetic wave having a differentfrequency than the frequency of the electromagnetic wave received by thefirst antenna; a second rectifying circuit formed on the siliconsubstrate, for rectifying a signal from one of the second antenna or thesecond coil; and a mono-stable multi-vibrator circuit whose input is asignal from the second rectifying circuit, wherein one of the firstantenna and the first coil performs power generation utilizing theenergy of the electromagnetic wave; the energy is stored in the storagecircuit; and the switching circuit is turned on for a defined period oftime determined by the mono-stable multi-vibrator circuit to connect thestorage circuit and the load, when power generation is performed by thesecond rectifier circuit after receiving an electromagnetic wave, whichhas a different frequency from the frequency of the electromagnetic wavereceived by the first antenna or the first coil, by one of the secondantenna or the second coil.

A power generation circuit using electromagnetic wave according to thepresent invention is effective since generation of a specific energy isnot needed to perform power generation.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a plan view showing a power generation circuit usingelectromagnetic wave according to a first embodiment of the presentinvention;

FIG. 2 is an example of the power generation circuit usingelectromagnetic wave according to the first embodiment of the presentinvention;

FIG. 3 is a power generation circuit using electromagnetic waveaccording to a second embodiment of the present invention;

FIG. 4 is the power generation circuit using electromagnetic waveaccording to the second embodiment of the present invention;

FIG. 5 is the power generation circuit using electromagnetic waveaccording to the second embodiment of the present invention;

FIG. 6 is the power generation circuit using electromagnetic waveaccording to the second embodiment of the present invention;

FIG. 7 is a power generation circuit using electromagnetic waveaccording to a third embodiment of the present invention;

FIG. 8 is a power generation circuit using electromagnetic waveaccording to a fourth embodiment of the present invention;

FIG. 9 is a power generation circuit using electromagnetic waveaccording to a fifth embodiment of the present invention;

FIG. 10 is a power generation circuit using electromagnetic waveaccording to a sixth embodiment of the present invention;

FIG. 11 is a power generation circuit using electromagnetic waveaccording to a seventh embodiment of the present invention; and

FIG. 12 is an example of a conventional power generation circuit usingelectromagnetic wave.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to solve the problems described above, power generation isperformed by utilizing electromagnetic wave in space for living in thisinvention.

Embodiments of the present invention are explained below with referenceto the drawings.

First Embodiment

FIG. 1 is a power generation circuit using electromagnetic waveaccording to a first embodiment of the present invention.

An antenna or a coil 2, a rectifying circuit 1, and a storage circuit 3are mounted on a substrate 10. A capacitor, for example, may be usedinstead of the storage circuit 3.

FIG. 2 shows a specific example of a power generation circuit usingelectromagnetic wave. A coil 2 serving as the antenna 2, a Schottkeybarrier diode (hereinafter called “SBD”) serving as the rectifyingcircuit 1 and a capacitor 3 serving as the storage circuit 3 areconnected therebetween.

The coil 2 receives the energy supplied from a commercially availableelectromagnetic wave such as an electromagnetic wave for a cellulartelephone, TV broadcasting, or FM radio broadcasting. The SBD 1rectifies a voltage generated in the coil 2 to inject electric chargeinto the capacitor 3.

Kind and strength of the commercially available electromagnetic wavediffer greatly depending upon location and time. However small and weakan available electromagnetic wave is, the circuit shown in FIG. 2 cancharge little by little the capacitor 3. Accordingly, even in thelocation of the weak electromagnetic wave, the capacitor 3 will becharged over a long period of time, and the charge is accumulated in thecapacitor 3. Consequently it is possible to drive a load by utilizingthe charge in the capacitor 3 by connecting the load across bothterminals of the capacitor 3.

Second Embodiment

FIG. 3 is a power generation circuit using electromagnetic waveaccording to a second embodiment of the present invention.

A coil 2, a SBD 1, and a capacitor 3 are connected similar to those ofFIG. 2. A source of a P-channel MOS transistor 6 is connected to apositive terminal of the capacitor 3, and a drain of the P-channel MOStransistor 6 is connected to a load 7. Agate of the MOS transistor 6 isconnected to a negative terminal of the capacitor 3.

Connecting in this way, the MOS transistor 6 turns on to connect theload 7 to the capacitor 3 in parallel and the energy of the capacitor 3can drive the load 7 when the voltage accumulating in the capacitor 3becomes higher than the threshold voltage of the MOS transistor 6.

The MOS transistor 6 is in an off-state when the voltage of the storedcharge in the capacitor 3 is less than the threshold voltage of the MOStransistor 6, and no electric power is consumed. In this circuitdetection of the voltage accumulated by electromagnetic wave can beperformed without electric power consumption, and the connection of theload can be controlled when the voltage of the capacitor 3 reaches agiven voltage. Adjustment of the threshold voltage of the MOS transistorenables the adjustment of the voltage for connecting the capacitor 3 andthe load 7.

In addition, as shown in FIG. 4, it is also possible to adjust thevoltage for connecting the capacitor 3 and the load 7; a MOS transistor9 having a drain connected to a gate is connected to a gate of the MOStransistor 6, and a high-resistance resistor 10 is connected between thegate and the source of the MOS transistor 6. In this circuit, connectionof the capacitor 3 and the load 7 is established when the capacitor 3 ischarged so that the voltage across the capacitor 3 reaches a voltageequal to the sum of the threshold voltage of the MOS transistor 6 andthe threshold voltage of the MOS transistor 9.

Further, as shown in FIG. 5, a drain and a source of a MOS transistor 11serving as a switch are connected to the drain and the source,respectively, of the MOS transistor 9 of FIG. 4 whose gate is connectedto the drain. When the capacitor 3 is charged to a voltage equal to thesum of the threshold voltages of the MOS transistor 6 and the MOStransistor 9, the transistor 11 serving as a switch is turned onaccording to a signal from a control circuit contained in the load 7 atthe moment when the capacitor 3 and the load 7 are connected.Accordingly, the connection between the capacitor 3 and the load 7 canbe maintained till the voltage of the capacitor 3 drops below thethreshold voltage of the MOS transistor 6.

Further, as shown in FIG. 6, an N-channel MOS transistor 8 can be usedas a substitute for a P-channel MOS transistor. In this case, a sourceof the MOS transistor 8 is connected to the negative terminal of thecapacitor 3, a gate of the MOS transistor 8 is connected to the positiveterminal of the capacitor 3, and the load 7 is connected to the positiveterminal of the capacitor 3 and to a drain of the MOS transistor 8. Inthis structure, when the voltage across the terminals of the capacitor 3becomes higher than the threshold voltage of the MOS transistor 8, theMOS transistor 8 turns on and thus connects the capacitor 3 and the load7.

As an application of the power generation circuit using electromagneticwave according to the present invention, failure diagnosis of amechanical component or an electrical component (such as a motor) can bedone without battery. For example, the resonant frequency, with whichpower generation is most effective, in FIG. 3 is set to the frequency ofan electromagnetic wave that are generated at the time when the failureoccurs to the mechanical component or to the electrical component. Inthis case, when the mechanical component or the electrical componentfails, an electromagnetic wave having a certain frequency will begenerated. Upon receiving the electromagnetic wave, the power generationcircuit according to the present invention generates power, and anelectric power is supplied to a circuit (load 7) which sends anotification of an abnormality of the mechanical part or the electricalpart. In this manner failure diagnosis of a mechanical component or anelectrical component can be done without battery.

Third Embodiment

FIG. 7 is a power generation circuit using electromagnetic waveaccording to a third embodiment of the present invention.

A rectifying circuit and elements such as a capacitor, a resistor, or aMOS transistor are fabricated on a silicon substrate 50 by siliconplanar process. In addition, a recess is formed in the silicon substrate50 by anisotropic dry etching of silicon such as deep reactive ionetching (DRIE), or by anisotropic wet etching employing a material suchas tetramethylammonium hydroxide (TMAH). When the recess is formed byDRIE, the recess is formed substantially perpendicular with respect tothe silicon substrate, as shown in FIG. 7. When the recess is formed bywet etching, the recess is generally formed with a certain angle withrespect to the substrate.

On the other hand, there is a projecting terminal on the antenna 2. Theprojecting terminal is inserted into the recess of the silicon substrate50. The depth and the size of the recess of the silicon substrate 50 areadjusted depending upon the size of the projecting terminal of theantenna 2 that is inserted into the recess.

As an example of a method of fixing the silicon substrate 50 with theantenna 2, a metal interconnection, an interconnection using highconcentration diffusion or a polysilicon interconnection is formed inadvance in the recess of the silicon substrate 50, the interconnection 5being connected to elements formed on a surface of the silicon substrate50. A low melting metal or a conductive adhesive 4 is provided to aportion in the recess of the silicon substrate 50 at which the terminalof the antenna 2 makes contact, when the antenna 2 is inserted into therecess. Then the antenna 2 is inserted into the recess of the siliconsubstrate 50 in this state, the projecting terminal of the antenna 2 andthe wiring 5 are electrically connected by the conductive adhesive 4. Asa result, the antenna 2 is electrically connected to the elements formedon the surface of the silicon substrate 50.

In prior art, the receiving sensitivity of an antenna may change greatlydepending upon the wiring length between the antenna and the rectifier.However, with this structure, the connection between the antenna and thesemiconductor element can be made with a minimum wiring length. Inaddition, the power generation circuit using electromagnetic wave can bemade smaller.

Further, according to the present invention, the power generation can bemade using not only commercially available electromagnetic waves such asthose generated from cellular telephones, TV broadcasts, and FM radiobroadcasts but also an electromagnetic wave which is generated byfluorescent light, off ice automation equipment or the like and whichfills a space of living. Furthermore, the power generation may also bepossible using a specific electromagnetic wave which is generated when amechanical component or an electrical component fails.

Further, although an example of a rectifying circuit and a storagecircuit is shown in FIG. 2, the present invention is not limited tothese circuits. Any structure may be employed using any means as long ashaving a rectifying function and a charge storing function.

Fourth Embodiment

FIG. 8 is a power generation circuit using electromagnetic waveaccording to a fourth embodiment of the present invention.

After an antenna or coil 2 receives an electromagnetic wave and powergeneration is performed, a rectifying circuit 20 performs rectification,converting an alternating current voltage into a direct current voltage,and a booster circuit 21 boosts the voltage level. In general, thebooster circuit 21 boosts the voltage to a level at which a load 7 canoperate since the voltage generated by the antenna or coil 2 is low whenthe electromagnetic wave is weak. The boosted voltage is accumulated inthe storage circuit 3. A voltage detector circuit 23 detects the voltageof the storage circuit 3. When the voltage of storage circuit 3increases to an arbitrary voltage determined by the voltage detectingcircuit, a switching circuit 24 turns from off to on, connecting thestorage circuit 3 and the load 7.

According to the present invention, even when power generation isperformed by a weak electromagnetic wave, the voltage is boosted to alevel sufficient to drive the load by the booster 21, and the boostedvoltage is detected by the voltage detecting circuit 23. After thevoltage has been reached to the voltage sufficient to drive the load,the voltage is supplied to the load 7 through the switching circuit 24.Accordingly, wrong operation of the load 7 can be positively prevented.

Further, electric power is supplied to the load 7 at an instant when theswitching circuit 24 turns on, there is a fear in that the voltage ofthe storage circuit 3 may decrease to cause the switching circuit 24 toreturn to off-state, and then the on-state and off-state may alternatelyappear. However, disposing hysteresis to the voltage detecting circuit23 can prevent such action.

Fifth Embodiment

FIG. 9 is a power generation circuit using electromagnetic waveaccording to a fifth embodiment of the present invention. Differing fromthe power generation circuit using electromagnetic wave shown in FIG. 8,output from the voltage detector circuit 23 is connected to amono-stable multi-vibrator circuit 25, and the mono-stablemulti-vibrator circuit 25 controls the switching circuit 24. In otherwords, a trigger signal is imparted to the mono-stable multi-vibrator 25by a signal having an arbitrary voltage detected by the voltagedetecting circuit 23, and the mono-stable multi-vibrator 25 turns on theswitching circuit 24 for a given period of time set in advance.

With this structure, it becomes possible to supply electric power to theload 7 for only a necessary period of time by setting the time periodheld in the mono-stable multi-vibrator so that the switching circuit 24is turned on only for a processing period during which the load canperform certain processes. Wasteful energy consumption of the storagecircuit 3 can thus be suppressed.

Sixth Embodiment

FIG. 10 is a power generation circuit using electromagnetic waveaccording to a sixth embodiment of the present invention. Differing fromthe power generation circuit using electromagnetic wave shown in FIG. 8,voltage generated by a second antenna or a second coil 26, not theoutput of the voltage detecting circuit 23, is rectified by a secondrectifying circuit 27, and the rectified voltage turns on the switchingcircuit 24.

For example, the first antenna or the first coil 2, the first rectifyingcircuit 20, and the booster circuit 21 is constructed so as to alwaysreceive an electromagnetic wave to store the electric power to thestorage circuit 3. In contrast, the second antenna or the second coil 26is constructed so as to react only to an electromagnetic wave having aspecific frequency to generate power. It is possible to connect thestorage circuit 3 and the load 7 by the switching circuit 24 only whenthe power is to be supplied to the load 7, by applying a specificelectromagnetic wave that reacts to the second antenna and when theelectromagnetic wave is received.

The frequency at which the second antenna effectively generates power(resonant frequency) is defined so as to correspond to a frequency of anelectromagnetic wave which is generated when a mechanical component oran electrical component is failed. As a result, the second antenna ofthe present invention generates electricity when the mechanicalcomponent or the electrical component fails, and supplies the electricpower to the load 7; a circuit that notifies abnormality of themechanical component or the electrical component. Consequently, failuredetection of the mechanical component or the electrical component can beperformed without battery.

Seventh Embodiment

FIG. 11 is a power generation circuit using electromagnetic waveaccording to a seventh embodiment of the present invention. Differingform the power generation circuit using electromagnetic wave shown inFIG. 10, a trigger signal, which is generated by the second antenna orthe second coil 26 and is rectified by the second rectifying circuit 27,is imparted to the mono-stable multi-vibrator 25. The switching circuit24 is turned on for a period of time set in advance by the mono-stablemulti-vibrator 25.

In the structure shown in FIG. 10, to hold the switching circuit 24 inan ON-state, it is necessary to keep generating a specificelectromagnetic wave to which the second antenna reacts, whereas in thestructure shown in FIG. 11, it is not necessary to keep generation ofthe specific electromagnetic wave.

As explained above, according to the present invention, it becomespossible to provide the power generation circuit using electromagneticwave that is capable of generating power without energy of the specificelectromagnetic wave.

It is possible to use the power generation circuit using electromagneticwave according to the present invention as a technique of constructing abattery less electric power source.

1. A power generation circuit using energy of an electromagnetic wave,comprising: one of an antenna or a coil for receiving an electromagneticwave; a rectifying circuit formed on a silicon substrate, for rectifyinga signal from the antenna or the coil; and a circuit for storing anoutput power from the rectifying circuit, wherein power generation isperformed by utilizing the energy of the electromagnetic wave; and theelectromagnetic wave is a commercially available electromagnetic wave.2. A power generation circuit using energy of an electromagnetic waveaccording to claim 1, wherein a source and a drain of an enhanced MOStransistor are connected to an output of the storage circuit and a loadrespectively; and control of connecting the storage circuit and the loadis performed by utilizing a threshold voltage of the enhanced MOStransistor.
 3. A power generation circuit using energy of anelectromagnetic wave according to claim 1, wherein a recess is formed inthe silicon substrate; a projecting terminal that conforms to a shape ofthe recess in the silicon substrate is formed on one of the antenna andthe coil; and an electrical connection is established between theantenna or the coil and an element formed on the silicon substrate byinserting the projecting terminal of the antenna into the recess in thesilicon substrate.
 4. A power generation circuit using energy of anelectromagnetic wave according to claim 2, wherein a recess is formed inthe silicon substrate; a projecting terminal that conforms to a shape ofthe recess in the silicon substrate is formed on one of the antenna andthe coil; and an electrical connection is established between theantenna or the coil and an element formed on the silicon substrate byinserting the projecting terminal of the antenna into the recess in thesilicon substrate.
 5. A power generation circuit using energy of anelectromagnetic wave according to claim 1, wherein the electromagneticwave exists in a space for living.
 6. A power generation circuit usingenergy of an electromagnetic wave according to claim 2, wherein theelectromagnetic wave exists in a space for living.
 7. A power generationcircuit using energy of an electromagnetic wave according to claim 3,wherein the electromagnetic wave exists in a space for living.
 8. Apower generation circuit using energy of an electromagnetic waveaccording to claim 4, wherein the electromagnetic wave exists in a spacefor living.
 9. A power generation circuit using energy of anelectromagnetic wave, comprising: one of an antenna or a coil forreceiving an electromagnetic wave; a rectifying circuit formed on asilicon substrate, for rectifying a signal from one of the antenna orthe coil; a booster circuit for boosting an output of the rectifyingcircuit; a storage circuit for storing an output power from the boostercircuit; a detecting circuit for detecting a voltage of the storagecircuit; and a switching circuit for connecting the storage circuit anda load, wherein power generation is performed utilizing the energy ofthe electromagnetic wave; and the switching circuit is turned on toconnect the storage circuit and the load when the detecting circuitdetects that the voltage of the storage circuit is equal to or greaterthan a defined voltage. 10.-12. (canceled)